Assembly of a Portable Video Receiving Ground Station

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By Scott Turnbull

This article discusses some alternatives and tips for setting up a ground station for receiving down linked video broadcasts.

It is a follow up to my article from last year that described the construction of a patch antenna for use in receiving broadcasts. That antenna works well with the BoosterVision mini-gear cam available online. An apparently similar broadcasting camera and receiver has been seen on the shelves of WalMart at a price competitive with BoosterVision's.

Once you have purchased a wireless video broadcasting camera and receiver, there still remains the question of what to connect the receiver to. In my first summer of video flights I worked with a minimal budget while proving to myself the reliability and quality of the signal received from the onboard video camera.

The ground system I first assembled on a budget was not portable as much as it was luggable. The typical broadcast video receiver outputs video and audio signals on separate RCA jacks. I purchased a standard household VHS VCR with RCA inputs for $5 at a garage sale. I spent another $5 for a small black and white television with RCA jacks at a Thrift Store. To power the VCR I purchased a Power Inverter that converts 12VDC to 120VAC. This was originally to be plugged into a car's power socket. Knowing that I wouldn't always be near my car, I purchased a small, sealed 12VDC car booster battery. The video receiver and television could be run directly from 12VDC, but since I already had the Power Inverter, I used the "wallwwart" powersupplies to power all the equipment from a single switched power strip.

This system was inexpensive enough, costing less than the BoosterVision camera, but it required a large tub to carry it all, and a protected area to set it up. One of the downsides was that I could not confirm the quality of broadcast signal while powering up the camera at the launch pad. I would need to enlist a volunteer to monitor the receiver, or scurry back to it to see if the onboard camera was broadcasting clearly. Another problem was that I needed to either start the recorder early, or stay near it to start it when my camera's turn for launch came up.

After refining my strap on camera pod system, I was satisfied with the quality of captured video. The time came to refine the ground station to make it easier to use. I decided that a camcorder capable of recording the video signal was the way to go.

I researched CamCorders, assembling a list of models that supported "line in". That capability is what enables the CamCorder to record data from an outside source. The new ones that had it were all relatively expensive, costing several hundred dollars for basic models. It seems that fewer and fewer models are supporting external source recording. I looked in a slightly different class of electronics and came across my answer, the Aiptek MPVR. It is a solid state media player and video recorder. It can serve as a digital video camcorder, 3MP digital camera, digital video recorder, audio recorder, mp3 player and USB harddrive. I purchased mine for $150 from CircuitCity, but they are widely available from other sources for slightly less. As with all things digital, the price falls off quickly as follow-up models reach the market.

Of particular interest to me were the MPVR capabilities as a digital video recorder, aka DVR. The video from external sources can be captured as 640x480x30fps to an SD memory card. The videos are Mpeg4 encoded. The built in 2.4" color LCD can be used to monitor and play back recordings. The built in speaker or earphone jack can be used to monitor audio. As can be seen in the attached photos, the MPVR is actually smaller than the BoosterVision video receiver. It is powered by rechargeable Lithium Ion batteries that are compatible with some models of Sanyo cellphones.

The final step in making my receiving ground station portable was obtaining a small 12VDC power source for the receiver. I took the low-tech, and low capacity route of using 8 rechargeable Lithium Ion AA batteries in a battery holder purchased at RadioShack. I needed to solder a suitable power connector to a 9V battery clip to connect the battery pack to the receiver.

With the new, fully portable receiving and recording station I can hold the system in one hand, carry it to the pad, and review the quality of the camera broadcast as the rocket is being prepped. I can then loiter on the flight line, far from my car, and monitor the camera signal. Just prior to launch I press the record button, and am able to wander off in search of my rocket while still carrying the receiving station. When I'm not receiving video from the broadcasting camera, I can disconnect the cable and use the MPVR as either a standard camcorder or digital camera.

Since I have a digital camera, camcorder, audio recorder, and video recorder in my hand, I can fully document the flight from prep to the walk back in after recovery.

To help ruggedize my newly portable patch antenna, I sandwiched it between the plastic lids from two inexpensive food storage containers. The container lids still snap onto the container that is large enough to hold the receiver for storage. I even went as far as crafting a tripod mount on the receiver, and mounting a bolt on a hardhat. In times of great need I could mount the receiver on the hardhat, thus freeing my hands while the recorder is running. I’m not sure the world is ready for that fashion statement, so don’t hold your breathe waiting to see any pictures of that configuration in use.

For longer trips, there’s always the issue of how long batteries will last. I have not exhausted either the MPVR battery, nor the 8AA power pack in a casual day’s shooting. I know that the 1GB SD card I use with the MPVR can record 40minutes of nonstop video.

There is some additional support equipment that I bring on long trips. I pack an extra set of 8 AA batteries and a charger to charge them. I also pack a spare battery for the MPVR and the charger to charge it. Each charger can work from 110AC, or 12VDC, so I still pack that sealed car booster battery. The point to remember is that this is backup equipment, and is not needed for a day’s taping at a launch. The MPVR also comes with cables to connect the recorder either to a laptop, or to video inputs of a recorder or large screen. What better way to review the day’s launch festivities, than to play back the pictures, ground based movies, and downlinked videos in the hotel lounge? While you’re there with the MPVR, you can take some more pictures of your fellow fliers enjoying the Apres Flight

GUEST's OPINION:
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